Hand job is a term used to for when someone pleasures a penis by going back and fourth using their hands. It can be fast or slow, tight or loose in grip based on what an individual prefers. During masturbation people with penis use their hand to experience pleasure. There are various ways to give hand jobs and communication and exploration with your partners in important to understand what works for your or your partner. Use of lubricant for handjobs is not uncommon. Hand job is not limited to the penis, as the testicles or balls are also a high pleasure points for many people.
Sources:
https://www.healthline.com/health/healthy-sex/how-to-give-a-handjob#techniques